pattern – Anole Annals

Female Anolis polylepis. Photo from http://www.wildherps.com/species/A.polylepis.html

In many species of anoles, females within a population exhibit sometimes strikingly different back patterns. A recent paper showed that there is interesting variation in the incidence of such variation: mainland and Lesser Antillean anoles exhibit it much more than Greater Antillean anoles, and within regions, some clades are more polymorphic than others. Although closely related species tend to be similar, this trait has been evolutionarily labile, evolving an estimated 28 times.

The occurrence of this variation raises the question: what’s it for? The most detailed study of the question was Schoener and Schoener’s examination of female polymorphism in Anolis sagrei in the Bahamas. By looking both within and between populations, they concluded that this polymorphism was related to crypsis. In particular, females with stripes tend to occur on narrow diameter branches, where the stripes help them blend in. Calsbeek and Cox have more recently examined the same species, finding most recently that different patterns don’t seem to vary in fitness, though they did not examine whether females with different patterns occurred in different parts of the microhabitat.

The only other recent work on this topic was conducted on A. polylepis in Costa Rica by Steffen.

In many species of anoles, females vary in their back patterning, some gaudily adorned with saddles, diamonds, or crosses, others sporting simple lines and speckles, some sad lasses with no markings at all. Although such female pattern polymorphism has long been noted and its adaptive significance studied (for example, here), no one has compiled a list of which species exhibit it and which don’t, much less examined patterns of FPP evolution.

Until now. In a very nice paper, Paemelaere et al. have surveyed the literature and recorded the presence or absence of of FPP in 179 anole species. They find a wide variety of interesting findings. First, there is phylogenetic signal: closely-related species tend to be similar in the presence or absence of FPP. Nonetheless, second, FPP has evolved and been lost many times—overall, at least 28 evolutionary transitions, with more gains than losses. The ancestral condition, incidentally, appears to be an absence of FPP. Third, there is great biogeographical heterogeneity (see figure above). FPP is far-and-away most common among mainland anoles, and is also reasonably common in the Lesser Antilles, but much less common in the Greater Antilles. Within the mainland anoles, it is particularly members of the Norops club that have FPP; much less among dactyloids. However, Norops also occurs on Cuba and Jamaica, and there they don’t exhibit much FPP.

One additional interesting pattern not remarked upon by Paemelaere is that among Greater Antillean species, FPP occurs primarily in trunk-ground anoles, having evolved at least three times independently on different islands (in three members of the sagrei clade on Cuba; A. cristatellus on Puerto Rico; and three members of the cybotes clade on Hispaniola).

Tag: pattern

Variation in Habitat Use by Females with Different Back Patterns

The Evolution of Female Pattern Polymorphism